1. Field of the Invention
The present invention relates to a camera, and more particularly, to an omni-directional stereo camera for making a panoramic image, and a control method thereof.
2. Description of the Related Art
In various business offices such as buildings, banks, apartments or the like, the surroundings, parking areas, or the like are used by the by the public. In these areas, a closed circuit TV (CCTV) is installed to monitor the areas and to secure the safety of the public. A conventional monitor camera employed in the CCTV can capture an image of a very restricted area within a predetermined angle of view. Thus, if it is desired to capture and monitor the restricted area along with a wider area, it is necessary to install a greater number of cameras. However, by doing so, costs for installing the cameras and time for installation both increase.
A panoramic camera can capture a wider area because this device has a wider viewing angle than that of a general camera. However, the function of the panoramic camera is also restricted because this camera unable to capture an image in all directions, i.e. 360 degrees. In order to improve the angle of view, an omni-directional camera for capturing an image in all directions, i.e. 360 degrees, is used. The omni-directional camera can take a photograph of the surroundings of the camera in a complete 360 degree view. Thus, since the omni-directional camera can take a photograph in almost every direction except for a concealed place, even when a single omni-directional camera is installed, the omni-directional camera is very useful as a monitor camera.
FIG. 1 is a view illustrating a conventional single viewpoint omni-directional camera. As shown in FIG. 1, the conventional omni-directional camera is designed such that light reflected by a mirror 102 is projected to an image forming surface of an image sensor 104. In other words, a light at a certain position X in space is reflected from a position Xmir of the mirror 102 having a parabola-shaped surface and is projected to a position Ximg on the image sensor 104. Like this, light from a large portion of positions adjacent to the mirror 102 is reflected by the surface of the mirror 102 and is projected to the image forming surface of the image sensor 104 so that the image sensor 104 combines the projected light to form a distorted circular omni-directional image projected onto the mirror 102. The omni-directional image is compensated by an image processor and is transformed into a perfect 360 degree panoramic image.
An omni-directional camera, which has a single point Omir in the mirror 102 at which all incident lights concentrate, is called a single viewpoint (SVP) omni-directional camera. Otherwise, an omni-direction camera, which has more than two points Omir at which incident lights of the mirror 102 concentrate, is called a non-SVP omni-directional camera. Since it is very difficult to actually implement the SVP omni-directional camera because of restrictions such as design, the angle of view, or the like, the non-SVP omni-directional camera, which is relatively easily implemented, is mainly used.
The SVP omni-directional camera takes a photograph of a plane style compensation pattern positioned in a space to obtain an image difference for obtaining the image difference between a distorted omni-directional image and a compensated complete panoramic image and to apply the image difference to the compensation. However, the non-SVP omni-directional camera must obtain a required image difference for the compensation after positioning a cylindrical compensation pattern at the surroundings of the non-SVP omni-directional camera.
FIG. 2 is a view illustrating the compensation using a space pattern carried out in the non-single viewpoint omni-directional camera. As shown in FIG. 2, a cylindrical compensator 202 on which uniform patterns are pictured is positioned around the camera to extract the distorted omni-directional image. Thus, in order to compensate the non-SVP omni-directional camera, the camera must be moved to the place where the compensator 202 is installed, or the compensator 202 must be moved to a place where the camera is installed. Since the movement and the installation is required in all cases, this camera is very inconvenient. Particularly, if the camera is installed at a very high place or an inconvenient place which a user or a manager has difficulty accessing, the inconvenience is further increased.